The proposed research involves a study of lens regeneration and neural retina regeneration from pigmented iris or retinal epithelium in urodele amphibians, primarily newts. It is hoped to obtain information concerning the stimuli which release the processes of metaplasia taking place and the role of trophic factors during the course of regeneration. Synthesis of macromolecules and cytological changes in the reacting tissues will also be studied. Some of the aspects being investigated are the ultrastructural changes during dedifferentiation of the iris and beginning lens differentiation in young and old larvae and ultrastructural and synthetic events involved in lens capsule formation as the lens regenerate enlarges; a study of any changes in the neural retina during lens regeneration that might be observable electron microscopically, or by means of fractionation and incorporation studies on neural retinal proteins; in vitro studies on stimulation of lens regeneration by different growth factors; and patterns of incorporation of tritiated uridine and amino acids during neural retina regeneration.